Take a first cut at cleaning up ifnet removal and multicast socket

panics, which occur when stale ifnet pointers are left in struct
moptions hung off of inpcbs:

- Add in_ifdetach(), which matches in6_ifdetach(), and allows the
  protocol to perform early tear-down on the interface early in
  if_detach().

- Annotate that if_detach() needs careful consideration.

- Remove calls to in_pcbpurgeif0() in the handling of SIOCDIFADDR --
  this is not the place to detect interface removal!  This also
  removes what is basically a nasty (and now unnecessary) hack.

- Invoke in_pcbpurgeif0() from in_ifdetach(), in both raw and UDP
  IPv4 sockets.

It is now possible to run the msocket_ifnet_remove regression test
using HEAD without panicking.

MFC after:	3 days

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/netinet/in.h b/sys/netinet/in.h
index f006ae3..eede911 100644
--- a/sys/netinet/in.h
+++ b/sys/netinet/in.h
@@ -572,6 +572,7 @@ int	 in_localaddr(struct in_addr);
 int	 in_localip(struct in_addr);
 char	*inet_ntoa(struct in_addr); /* in libkern */
 char	*inet_ntoa_r(struct in_addr ina, char *buf); /* in libkern */
+void	 in_ifdetach(struct ifnet *);
 
 #define	in_hosteq(s, t)	((s).s_addr == (t).s_addr)
 #define	in_nullhost(x)	((x).s_addr == INADDR_ANY)